BUG/MINOR: resolvers: Reset server IP when no ip is found in the response

BUG/MINOR: resolvers: Reset server IP when no ip is found in the response

For A/AAAA resolution, if no ip is found for a server in the response, the
server is set to RMAINT status. However, its address must also be
reset. Otherwise, it is still reported by the cli on "show servers state"
commands. This may be confusing.

This patch may be backported as far as 2.0.

(cherry picked from commit a8ce497aacd6871c6056baf5a30e04f021956a5c)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 7c129bba960aebec175b3fcf2d0ffa52d584552f)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>